What is the easyest way to tell which park brake diaphram is leaking. The bottom of the foot brake E10 has air coming out . It just started .It will bleed down to 60 PSI and stay there. Almost imposable to get it up to 120. Fred

When our parking brake diaphragm went bad the air blew out the brake relay valve. Get a soap bottle. Try to get enough air to apply the brakes and spray around the rings on the chambers. If it is a parking brake diaphragm, you will probably get bubbles on the back ring. It will also blow air out the bottom of the relay valve. If the inversion valve is bad, It can leak air also. When we changed one diaphragm, we changed the other side. It is probably just as old and they aren't that hard to change.

When I first got my 04 it would leak down if you kept your foot on the brake. It was a cut in one of the rear brake supply lines. The 04 at that time had a ICC park brake, which meant that if the air dropped the brake let go and the bus rolled off? i since put spring brakes on it.

I was worried that clamping the hose would damage them. I will try that tomorrow. I am pretty sure that it is the park diaphram as when i hook up the compresor and take the park brake off it slows down , But there is still air coming from bottom of tredal valve. Fred

On a DD3, there are 3 hoses. The one closest to the pushrod is to keep the parking brake lock from engaging the pushrod and should have pressure when parking brake is released. The middle hose is service brake and should only have presssure when service brake is applied. The rearmost hose is the parking brake diaphragm and should have pressure when the parking prakem is engaged. I use a pair of vice grips that had the small (approx. 1" diameter) pads on the jaws. Jack